Despite the many advantages and wide commercial usage of lithium-ion batteries, there remain substantial performance limitations and safety concerns. The most serious safety issue involves operating temperature range and stability. An increase in internal temperature of the battery cell can lead to internal pressure build up due to an accelerated reaction rate between the electrolyte and electrodes. Mechanical stress then damages the electrolyte and separator, resulting in an increased internal resistance and thermal runaway. The cell may then short circuit and possibly explode. Since Li-ion batteries self-heat naturally as they are operated (discharged or charged), developing Li-ion batteries with high temperature operation capability is vital for overall safety and reliability. Today's commercial Li-ion battery cells are typically unreliable if operated above 60° C., and virtually none can survive operation above 100° C.